CVE-2026-70318
Summary
by MITRE • 08/11/2026
Improper input validation in Microsoft Office Excel allows an unauthorized attacker to disclose information locally.
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Analysis
by VulDB Data Team • 08/11/2026
This vulnerability represents a critical security flaw in Microsoft Office Excel that stems from inadequate input validation mechanisms within the application's processing pipeline. The weakness manifests when Excel encounters malformed or untrusted input data during file parsing operations, particularly in spreadsheet formats that support complex data structures and formulas. Attackers can exploit this vulnerability by crafting specially designed Excel files that trigger improper handling of input parameters, leading to information disclosure on the local system where the vulnerable application executes.
The technical nature of this flaw aligns with common software security vulnerabilities categorized under CWE-20, which specifically addresses "Improper Input Validation" in software applications. When Excel processes maliciously constructed input, it fails to properly sanitize or validate the data before incorporating it into internal processing structures, creating opportunities for attackers to extract sensitive information from memory locations or system resources. This type of vulnerability operates at the intersection of application-level security and data integrity, where the boundary between legitimate user input and potentially harmful payloads becomes compromised.
The operational impact of this vulnerability extends beyond simple information disclosure, as it provides attackers with potential access to system-specific data that could be leveraged for further exploitation attempts. Local information disclosure can include sensitive metadata, memory contents, or system configuration details that might reveal network topology, user credentials, or application state information. The attack vector typically involves social engineering campaigns where users are诱导 to open malicious Excel files through email attachments, malicious websites, or compromised file sharing platforms.
From an adversarial perspective, this vulnerability fits within the broader ATT&CK framework under the technique T1059.005 for "Command and Scripting Interpreter: Visual Basic", which describes how attackers can leverage Office applications to execute malicious code through macro functionality or similar mechanisms. The information disclosure aspect provides attackers with reconnaissance data that could inform subsequent phases of an attack, including privilege escalation attempts or lateral movement within compromised networks. Organizations should consider this vulnerability as part of a larger attack chain where initial access leads to reconnaissance and eventually to more sophisticated exploitation techniques.
Effective mitigation strategies must address both the immediate security gap and broader organizational security practices. Microsoft has released security updates that enhance input validation mechanisms within Excel's file processing routines, specifically targeting the conditions that allow improper data handling. Organizations should implement comprehensive patch management procedures to ensure timely deployment of these security updates across all endpoints running vulnerable versions of Office applications. Additionally, implementing strict file validation policies and user education programs can help reduce the likelihood of successful exploitation attempts through social engineering vectors. Network segmentation and monitoring solutions should also be deployed to detect anomalous behavior patterns that might indicate exploitation of this vulnerability or similar input validation flaws in other software components.